Application of Adaptive Materials and Coatings to Increase Cutting Tool Performance: Efficiency in the Case of Composite Powder High Speed Steel

Round 1

Reviewer 1 Report

1. The current study investigates the applicability of several types of adaptive materials and coatings that are using in cutting tools. The aim is to determine their performance to heat and power action during the cutting process in order to prolong tool life. The authors prepare HSS tools which contain refractive compounds from which were tested on milling steel. The authors also study the frictional behaviour of the tools. The author report increases in tool life by 200% and improvement in surface finish of the machined material.
2. The abstract reads well but need some modifications, first please avoid using excessive unnecessary wording. For example, line 17 “through a complex” I feel this is not necessary here and can be rephrase in a more simple and shortened way.
3. In line 13 “to react and adapt to external heat and power influences” this sentence is kind of confusing, are these smart materials? What do you mean by adaptive materials? I never heard of such during my work on many machining projects. From reading the manuscript, this work is simply testing cutting tools and cutting tool coatings in milling tests of steel. This is the best way to describe without the overstating some sentences which appear to be misleading.
4. Line 14 “thereby preserving the cutting tool's working capacity for a longer time” this sentence is so long, it can be shortened to “thereby improving tool life”. That is all, please keep it simple. Using excessive wording to describe something is not recommended in scientific manuscripts.
5. The authors should answer the following question in the abstract: Please consider reviewing the abstract and highlight the novelty, major findings and conclusions. Please make sure to specifically mention some findings, I don’t see any except one which is very generic about tool life and roughness you said you compared three materials what did you find from them, it seems there is a comparison taking place there, what about friction and temperature which you also analysed, all this is missing from the introduction results?
6. The introduction is very poor, it is very basic and generic, there is not in-depth reporting of the past literature review, this must be updated, and additional paragraphs must be added to highlight this issue. The authors should report on past studies similar to their work or closely related to it. Report what they did and what were their main findings and explain how their current work brings new knowledge and difference to the field.
7. At the end of the introduction the authors are encouraged to answer the following question: Please consider reviewing the abstract and highlight the novelty, major findings and conclusions.
8. At the end of the introduction the authors should briefly summarise again what was done in their work.
9. Line 74-374 these sentences are not suitable for the materials and methods section, please only focus on what you did in this section instead of adding some generic text. (please either remove it or move it to the introduction).
10. I am now confused about the nature of this article, is this a review article or are the authors summarising past work of other others, the materials and methods section does not read well at all! There is a lot of literature which is more suited for the introduction but not in here. Please carefully revised the materials and method section and follow the recommended guidelines set by the journal.
11. Line 74-374 this is a very long literature review, it is more suited for a review chapter in a thesis or a report but in a scientific paper, please reduce it or remove it, a lot of it is not suitable for journal articles.
12. Ok now I start to see where the materials and methods section starts, it starts from line 375. Please make sure that this is the first paragraph for this section, all the above is not suitable here. Move it introduction (part of it) or remove it completely.
13. Line 375 please avoid using we or our or us in the manuscript.
14. Line 382 “Preliminary studies carried out at MSTU "STANKIN" this is confusing, where are these preliminary studies? Can you reference them please or did you do them on your own? If yes then please show them to us so we could check them out.
15. Table 1, did the authors measure these properties or they were taken from somewhere in the literature?
16. Line 395 “an accurate” remove this it is unnecessary wording.
17. Again I am confused, why the authors report friction data in Table 1 and then they state they conduct friction tests in Table 2? What is the point if you already know the friction range of the studies materials.
18. Line 408 “Special samples” what is special about them? Please avoid using excessive wording or unnecessary ones that do not add any value to the manuscript content.
19. Extensive editing of English language and style required
20. The authors should add images and figures of the test equipment and machines used in the current study, also add some pictures of the fabricated cutting tools.
21. How many times each tool was tested? Did you repeat the tests to ensure repeatability?
22. Add some text and arrows to Figure 4 to tell the readers what they are looking at in there.
23. Line 464 “differ significantly” this is very obvious they are different materials?
24. Line 464 please avoid using first person in the manuscript. Check this elsewhere.
25. Caption of Figure 6, please add the (1) before the sentence not after it.
26. 100% HSS (1); 80% HSS, 20% TiC (2)à (1) 100% HSS; (2) 80% HSS, 20% TiC, or even better adda legend in the figure itself.
27. In section 3.3, what I want to see is critical discussion on why 20% TiCN tools outperformed other tools, which is obviously because of its better mechanical properties and maybe thermal conductivity? What does the literature say? Also how about the chemical reactivity of these materials with steel? This can also help explain the wear and surface roughness results you reported.
28. Line 536 please remove “dangerous section” this is not appropriate way of describing it, just simple say “cutting zone at the tool-chip interface” or similar wording which is more relevant in machining science.
29. Line 549 “As can be seen from” as it can be seen, “it” is missing here.
30. Line 565 “The results obtained during tribological tests are fascinating” this is inappropriate sentence, please remove it.
31. The results are merely described and is limited to comparing the experimental observation. The authors are encouraged to include a discussion section and critically discuss the observations from this investigation with existing literature.
32. This paper contains so many paragraphs which can be removed without affecting the quality of the manuscript. This study is simply studying the performance of different tool materials, that’s all, there is a lot exaggeration in many sections, the paper can be easily reduced from 26 pages to 15 or less when removing all the unnecessary paragraphs.

Author Response

Response to Reviewer 1 Comments

Dear reviewer,

Thank you very much for your kind evaluation of our work. We do agree with all your proposals and comments and have modified the manuscript according to them. The revised fragments are marked green.

We hope that with your comments the manuscript will be suitable for publishing in Coatings and will attract many potential readers of the journal.

Kind regards,

Authors.

Point 1: The current study investigates the applicability of several types of adaptive materials and coatings that are using in cutting tools. The aim is to determine their performance to heat and power action during the cutting process in order to prolong tool life. The authors prepare HSS tools which contain refractive compounds from which were tested on milling steel. The authors also study the frictional behaviour of the tools. The author report increases in tool life by 200% and improvement in surface finish of the machined material.

Response 1: Thank you for your deep understanding of the research subject and kind evaluation of our work.

Point 2: The abstract reads well but need some modifications, first please avoid using excessive unnecessary wording. For example, line 17 “through a complex” I feel this is not necessary here and can be rephrase in a more simple and shortened way.

Response 2: Thank you for pointing it; the abstract is revised.

BEFORE:

Furthermore, through a complex of metallophysical studies (study of temperature fields by the method of a semi-artificial microthermocouple, analysis in the surface layer of secondary structures by spectrometry methods, the study of frictional interaction by the method of high-temperature tribometry, etc.), as well as laboratory performance tests, it was shown that the characteristics of the tool material under the influence of external loads, adaptation of the surface layer to the conditions of heat-power exposure and, as a consequence, an increase in tool life up to 2 times and a significant decrease in the roughness of the workpiece.

NOW:

The characteristics of the tool material under the influence of external loads and adaptation of the surface layer to the heat-power exposure conditions were shown by the study of temperature fields using a semi-artificial microthermocouple method, spectrometry analysis of the secondary structures of the surface layer, frictional interaction study by high-temperature tribometry study and laboratory performance tests. Consequently, an increase in tool life was up to 2 times, and a significant decrease in the workpiece roughness was shown.

If it looks better, we will be pleased to know. Otherwise, we can revise it further according to the reviewer's comments.

Point 3: In line 13 “to react and adapt to external heat and power influences” this sentence is kind of confusing, are these smart materials? What do you mean by adaptive materials? I never heard of such during my work on many machining projects. From reading the manuscript, this work is simply testing cutting tools and cutting tool coatings in milling tests of steel. This is the best way to describe without the overstating some sentences which appear to be misleading.

Response 3: Thank you for your attention to the terms and research subject. When we talk about adaptive materials and coatings in our work, we wanted to confuse anyone in any way.

It is indicated in terms 35-39: «One of the most promising and dynamically developing scientific approaches aimed at solving the above problem, within the framework of which the most authoritative research groups around the world are working, is the development and use of adaptive materials and coatings, characterized by a particular structural-phase state in bulk and close to the surface layers [1-4]».

Next, the terminology is clarified (lines 40-41): «Scientists and specialists use various terms such as adaptive, self-organizing, selfhealing, intelligent, "chameleons" to designate such materials and coatings [5-10]».

Then, we have specified what the authors mean by these terms, lines 41-45: «They have a "common denominator," which means the ability to react and adapt to operational loads (wear, damage, thermal power conditions, stress-strain state, etc.) with all the variety of existing terms, thereby allowing the functionality of a machine-building product and ensure the operability of the entire system as a whole [11-14]».

We appreciate the reviewer's opinion, and the terms "intelligent" and "smart" were excluded from the manuscript text. However, the term "adaptive" cannot be wholly excluded since we did not introduce this term. It was introduced into scientific circulation less than ten years ago when the first works in this direction were published. In the list of references, we have provided a detailed list of authoritative works, in particular,

1. Muratore, C.; Voevodin, A.A. Chameleon Coatings: Adaptive Surfaces to Reduce Friction and Wear in Extreme Environments. Annu. Rev. Mater. Res. 2009, 39, 297–324.
2. Pogrebnjak, A.D., Bagdasaryan, A.A.; Pshyk, A.; Dyadyura, K. Adaptive multicomponent nanocomposite coatings in surface engineering. Physics-Uspekhi 2017, 60(6), 586-607.
3. Sergevnin, V. S.; Blinkov, I.V.; Volkhonskii, A.O.; Belov, D. S.; Chernogor, A.V. Structure formation of adaptive arc-PVD Ti-Al-Mo-N and Ti-Al-Mo-Ni-N coatings and their wear-resistance under various friction conditions. Surf. Coat. Technol. 2019, 376, 38-43.
4. Yuan, J.; Yamamoto, K.; Covelli, D.; Tauhiduzzaman, M.; Arif, T.; Gershman, I.S.; Veldhuis, S.C.; Fox-Rabinovich, G.S. Tribo-films control in adaptive TiAlCrSiYN/TiAlCrN multilayer PVD coating by accelerating the initial machining conditions. Surf. Coat. Technol. 2016, 294, 54–61.
5. Zekonyte, J.; Polcar, T. Friction Force Microscopy Analysis of Self-Adaptive W-S-C Coatings: Nanoscale Friction and Wear. ACS Appl. Mater. Interfaces 2015, 7(38), 21056-21064.

Unfortunately, we are not the first in the field of adaptive materials, but our research is not limited to trivial durability tests.

The starting point for research like ours is fundamental work showing that an external impact on the surface layer of a solid body (tool) causes its immediate response to adapt to external conditions and activate a protective reaction (barrier). The thin surface layer of the tool undergoes pronounced changes in the process of heat-power action. For example, during the cutting tool operation, the authors have repeatedly observed the formation of non-stoichiometric amorphous oxide films and other secondary (new) compounds. It will be possible to make a scientifically grounded choice of architecture, chemical, and phase composition of the coating for specific operating conditions and ensure the maximum possible wear resistance, having studied and understood the essence of the changes. It turns out that the critical stage of such studies will be the analysis of the nearby surface layer of the tool, which is carried out after the tests (heat-power effect, by nature close to the operating conditions), i.e., the modified surface layer in the "tool-workpiece" contact zone is comprehensively studied after their interaction. In our case, we applied secondary ion mass spectrometry to the worn out pads of the tool—decisions on the creation of new tool materials based on composite powder HSS can be made based on the obtained results.

Point 4: Line 14 “thereby preserving the cutting tool's working capacity for a longer time” this sentence is so long, it can be shortened to “thereby improving tool life”. That is all, please keep it simple. Using excessive wording to describe something is not recommended in scientific manuscripts.

Response 4: Thank you for noticing it. The fragment is revised.

Point 5: The authors should answer the following question in the abstract: Please consider reviewing the abstract and highlight the novelty, major findings and conclusions. Please make sure to specifically mention some findings, I don’t see any except one which is very generic about tool life and roughness you said you compared three materials what did you find from them, it seems there is a comparison taking place there, what about friction and temperature which you also analysed, all this is missing from the introduction results?

Response 5: Thank you for your suggestion; it is revised:

BEFORE:

The paper proposes a classification of the types of adaptive materials and coatings for tool purposes, showing the ability to adapt to external heat and power influences, thereby improving tool life. The effectiveness of the use of adaptive materials is demonstrated by the example of one of the technological approaches - the creation of cutting tools from composite powder high speed steels containing refractory compounds such as TiC, TiCN, and Al₂O₃, and its use in milling 41CrS4 steel. The characteristics of the tool material under the influence of external loads and adaptation of the surface layer to the heat-power exposure conditions were shown by the study of temperature fields using a semi-artificial microthermocouple method, spectrometry analysis the secondary structures of the surface layer, frictional interaction study by high-temperature tribometry study and laboratory performance tests. Consequently, an increase in tool life was up to 2 times, and a significant decrease in the workpiece roughness was shown.

NOW:

The paper proposes a classification of adaptive materials and coatings for tool purposes, showing the ability to adapt to external heat and power influences, thereby improving tool life. Creating a cutting tool made of composite powder high speed steels containing refractory TiC, TiCN, and Al₂O₃ compounds for milling 41CrS4 steel demonstrated the effectiveness of the adaptive materials. The tool material characteristics under the external loads' influence and the surface layer adaptation to the heat-power exposure conditions were shown by the temperature fields study using a semi-artificial microthermocouple method (the level of fields is reduced by 20-25% for 80%HSS+20%TiCN), frictional interaction high-temperature tribometry (the coefficient of friction did not exceed 0.45 for 80%HSS+20%TiCN at +20˚C and 600˚C), laboratory performance tests, spectrometry of the surface layer secondary structures. Spectral analysis shows the highest spectrum intensity of TiC₂ after 5 min of running in. After 20 min of milling (V = 82 m/min, f = 0.15 mm/tooth), dicarbide decomposes and transit to thermally stable secondary phases films of good lubricity such as TiO (maximum) and TiN (partially). An increase in tool life was up to 2 times (> 35 min for 80%HSS+20%TiCN), and a decrease in the roughness was up to 2.9 times (Ra less than 4.5 µm after 25 min of milling).

Point 6: The introduction is very poor, it is very basic and generic, there is not in-depth reporting of the past literature review, this must be updated, and additional paragraphs must be added to highlight this issue. The authors should report on past studies similar to their work or closely related to it. Report what they did and what were their main findings and explain how their current work brings new knowledge and difference to the field.

Response 6: Thank you, the introduction is revised.

Point 7: At the end of the introduction the authors are encouraged to answer the following question: Please consider reviewing the abstract and highlight the novelty, major findings and conclusions.

Response 7: Thank you, the novelty is added at the end of the introduction.

Point 8: At the end of the introduction the authors should briefly summarise again what was done in their work.

Response 8: Thank you for pointing it, it is revised.

Point 9: Line 74-374 these sentences are not suitable for the materials and methods section, please only focus on what you did in this section instead of adding some generic text. (please either remove it or move it to the introduction).

Response 9: The classification is moved into the section of discussion since it is original material that was never published before.

Point 10: I am now confused about the nature of this article, is this a review article or are the authors summarising past work of other others, the materials and methods section does not read well at all! There is a lot of literature which is more suited for the introduction but not in here. Please carefully revised the materials and method section and follow the recommended guidelines set by the journal.

Response 10: Thank you for your attention to the structure of the article. It is revised.

Point 11: Line 74-374 this is a very long literature review, it is more suited for a review chapter in a thesis or a report but in a scientific paper, please reduce it or remove it, a lot of it is not suitable for journal articles.

Response 11: Thank you for your efforts in making the manuscript better. It is revised.

Point 12: Ok now I start to see where the materials and methods section starts, it starts from line 375. Please make sure that this is the first paragraph for this section, all the above is not suitable here. Move it introduction (part of it) or remove it completely.

Response 12: Thank you for your suggestion. It is revised.

Point 13: Line 375 please avoid using we or our or us in the manuscript.

Response 13: Thank you, it is revised.

 Point 14: Line 382 “Preliminary studies carried out at MSTU "STANKIN" this is confusing, where are these preliminary studies? Can you reference them please or did you do them on your own? If yes then please show them to us so we could check them out.

Response 14: Thank you. The fragment is revised.

Point 15: Table 1, did the authors measure these properties or they were taken from somewhere in the literature?

Response 15: Thank you for your question, the data of the obtained CPHSS are not available in the literature and were pre-controlled in laboratories of the university. The relevant passage is added.

 Point 16: Line 395 “an accurate” remove this it is unnecessary wording.

Response 16: Thank you, it is revised.

 Point 17: Again I am confused, why the authors report friction data in Table 1 and then they state they conduct friction tests in Table 2? What is the point if you already know the friction range of the studies materials.

Response 17: Thank you for your attention to the details. Pre-controlled average data gives the common impression to the researchers and readers on parameters of the obtained tool material samples that were further tested in the conditions close to the conditions of the actual exploitation tests to obtain data on time graphs.

Point 18: Line 408 “Special samples” what is special about them? Please avoid using excessive wording or unnecessary ones that do not add any value to the manuscript content.

Response 18: Thank you. It is revised.

Point 19: Extensive editing of English language and style required

Response 19: Thank you, the text is revised.

Point 20: The authors should add images and figures of the test equipment and machines used in the current study, also add some pictures of the fabricated cutting tools.

Response 20: Thank you for pointing, the image of the cutting insert is provided in Figure 3.

Point 21: How many times each tool was tested? Did you repeat the tests to ensure repeatability?

Response 21: Thank you for your question. Sixteen samples of each tool material were tested. All experiments were reproduced five times to obtain data. The relevant passage is added.

Point 22: Add some text and arrows to Figure 4 to tell the readers what they are looking at in there.

Response 22: Thank you, it is revised.

Point 23: Line 464 “differ significantly” this is very obvious they are different materials?

Response 23: Thank you, it is revised.

Point 24: Line 464 please avoid using first person in the manuscript. Check this elsewhere.

Response 24: Thank you, it is revised.

Point 25: Caption of Figure 6, please add the (1) before the sentence not after it.

Response 25: Thank you, it is revised.

Point 26: 100% HSS (1); 80% HSS, 20% TiC (2)à (1) 100% HSS; (2) 80% HSS, 20% TiC, or even better adda legend in the figure itself.

Response 26: Thank you, the figure is revised.

Point 27: In section 3.3, what I want to see is critical discussion on why 20% TiCN tools outperformed other tools, which is obviously because of its better mechanical properties and maybe thermal conductivity? What does the literature say? Also how about the chemical reactivity of these materials with steel? This can also help explain the wear and surface roughness results you reported.

Response 27: Thank you, the relevant passage is added:

The best values for samples containing 20% TiCN can be explained by the specific physical and mechanical properties of this two-phase compound, primarily determined by the nature of interatomic bonds depending on the ratio of carbon and nitrogen atoms [1]. Some nitrogen atoms are replaced by carbon atoms in titanium carbonitride, forming unlimited TiN-TiC solid solutions. Titanium nitride has the same crystal lattice as titanium carbide, and it is capable of replacing it isomorphically [2]. TiCхNy compounds [3, 4] formed in the structure of CPHSS samples combine the advantages of carbide and nitride phases. The hardness of titanium carbonitride even slightly exceeds the value for titanium carbide when the plasticity is not inferior to that for titanium nitride (which is extremely important for the tool's operation during milling when the risk of chipping of the cutting edges increases). Titanium carbonitride inclusions have high thermodynamic stability and are closer to HSS in terms of thermal expansion coefficient. Besides, the improved performance for specimens with 20% TiCN compared to 20% TiC results from a lower affinity for iron-containing steels and alloys and a lower adhesive activity when heated [2-4]. The fact that the introduction of Al2O3 particles into a powder composition based on TiC somewhat improves the characteristics of CPHSS, but at the same time is inferior to samples with TiCN additives, indicates the need for separate studies related to the optimization of the compositions of powder mixtures during sintering of experimental instrumental materials.

 References

• Ivashchenko V.I.; Turchi P.E.A.; Gonis A.; Ivashchenko L.A.; Skrynskii P.L. Electronic origin of elastic properties of titanium carbonitride alloys. Metall. Mater. Trans. A 2006, 37, 3391–3396.
• Soković M.; Bahor M. On the inter-relationships of some machinability parameters in finish machining with cermet TiN (PVD) coated tools. Mater. Process. Technol. 1998, 78, 163–170.
• Chen R.; Tu J.P.; Liu D.G.; Mai Y.J.; Gu C.D. Microstructure, mechanical and tribological properties of TiCN nanocomposite films deposited by DC magnetron sputtering. Surf. Coat. Technol. 2011, 205, 5228–5234.
• Lengauer W.; Scagnetto F. Ti(C,N)-Based Cermets: Critical Review of Achievements and Recent Developments. Solid State Phenom. 2018, 274, 53-100

Point 28: Line 536 please remove “dangerous section” this is not appropriate way of describing it, just simple say “cutting zone at the tool-chip interface” or similar wording which is more relevant in machining science.

Response 28: Thank you, it is revised.

Point 29: Line 549 “As can be seen from” as it can be seen, “it” is missing here.

Response 29: Thank you for your attention to such details. Both ways are grammatically correct. “As can be seen” is more common in the scientific publications of native speakers than “As it can be seen” since it appears less wording - https://textranch.com/191205/as-it-can-be-seen/or/as-can-be-seen/

 Point 30: Line 565 “The results obtained during tribological tests are fascinating” this is inappropriate sentence, please remove it.

Response 30: Thank you, we do agree; it is removed and revised.

Point 31: The results are merely described and is limited to comparing the experimental observation. The authors are encouraged to include a discussion section and critically discuss the observations from this investigation with existing literature.

Response 31: Thank you for your proposal. Usually, we provide the section of discussion as well. However, in the current form of the manuscript, if we add the discussion section, we are afraid that the article will be overloaded with data and wording since it is already an issue. We wanted to save our classification for publishing since it is original, and we wanted to be the first in this domain with our classification, and, at the same time, we already have more outstanding results in design and producing the tool. If the reviewer finds it suitable, we can move our classification from the introduction to the discussion section and add a few sentences to summarize our work (now it is subsection 1.4). In the current version, the discussion is mixed with the results.

Point 32: This paper contains so many paragraphs which can be removed without affecting the quality of the manuscript. This study is simply studying the performance of different tool materials, that’s all, there is a lot exaggeration in many sections, the paper can be easily reduced from 26 pages to 15 or less when removing all the unnecessary paragraphs.

Response 32: Thank you for your proposal. We agree that the current version of the manuscript is overloaded with data, and we wanted to publish our classification and the last experimental results simultaneously since the only classification is not enough for the scientific review. We have decided to remove Figure 1 since we have added another figure. In the current version, it is 27 pages.

Reviewer 2 Report

This paper presents the influence of refractory compounds on the cutting tool performance. Results are original and the paper was well written. Some suggestions are made for authors to improve their paper before the publication.

1. In Figure 6, the sample (2) containing 80% HSS and 20% TiC exhibited a different trend at 15 min and had the highest value at 20 min. Authors are suggested to explain this observation.
2. In Figure 8, authors mentioned three stages from running-in to steady-state wear and then to critical wear. It is suggested to indicate these three stages in terms of cutting time that is shown in Figure 8.
3. In Figure 10(a) and (b), authors showed the effect of temperature on the coefficient of friction. It is suggested that authors should provide explanations for the temperature effect and discuss the mechanisms. 

Author Response

Response to Reviewer 2 Comments

Dear reviewer,

Thank you very much for your kind evaluation of our work. We do agree with all your proposals and comments and have modified the manuscript according to them. The revised fragments are marked yellow.

We hope that with your comments the manuscript will be suitable for publishing in Coatings and will attract many potential readers of the journal.

Kind regards,

Authors.

Point 1: In Figure 6, the sample (2) containing 80% HSS and 20% TiC exhibited a different trend at 15 min and had the highest value at 20 min. Authors are suggested to explain this observation.

Response 1: Thank you for your proposal. We have revised the text of the manuscript and introduced some changes:

The CPHSS samples differ in many respects from the standard HSS, which was expected since the hardness of the latter one is lower than that of CPHSS, and the average friction coefficient over steel is higher than that of CPHSS. The results of testing a sample of 80% HSS and 20% TiC (Figure 6, curve 2) showed the maximum increase in the wear of the contact zone after 15 min of milling and by the end of the tests. The volume of abrasion even slightly exceeds the wear of a sample from traditional HSS. The intensity of material destruction under an abrasive action is largely determined by the ratio of the counterbody hardness and the test metal surface hardness in the contact zone. A sharp increase in the wear rate of an 80% HSS and 20% TiC sample can be associated with a decrease in the hardness of its surface layer at a certain moment. The specific structure of CPHSS (Figure 5), containing a significant amount of refractory inclusions of polyhedral and fragmentary shapes, undissolved in the steel bond, suggests that the level of hardness (and the intensity of abrasive wear directly related to it) of such a material is determined by the degree of preservation of the high-hardness carbide phase. It is most likely that over time and an increase in the volume of abrasion, hard and, at the same time, very brittle TiC particles (their ductility increases at temperatures above 600˚C) are not retained in the steel bond and crumble, significantly changing the conditions of contact interaction between the tool material and counterbody. For the other two studied CPHSS samples (Figure 6, curves 3 and 4), a high degree of safety in the steel bond of high-hardness components is ensured throughout the entire test cycle. However, it is too early to conclude the prospects of one or another CPHSS variant based on evaluating the resistance to abrasion without thermal action.

Point 2: In Figure 8, authors mentioned three stages from running-in to steady-state wear and then to critical wear. It is suggested to indicate these three stages in terms of cutting time that is shown in Figure 8.

Response 2: Thank you for your suggestion. The text of the manuscript and Figure 8 are revised according to the provided recommendations, the stages of wear development are highlighted:

Figure 8 shows the laboratory tests' results of the tool in milling 41CrS4 steel and gives a quantitative assessment of the dimensional wear of the cutting part and the roughness of the processed surface of the workpiece. It can be seen that the curves of the development of wear for CPHSS samples (Figure 8a) in time are of a classical nature, and they show mainly three stages "running-in (I) – steady-state wear (II) – critical wear (III)." At the same time, zone II is noticeably narrowed for a tool made from 100% HSS, and there is no pronounced transition to zone III. Curves of changes in the roughness of the workpiece (Figure 8b) correlate well with the curves of wear development: at the initial stage of testing during running-in (natural blunting) of the tool, no change in roughness is observed; upon transition to the normal wear zone, there is a gradual increase in the contact area of the rear surface of the tool with the surface of the workpiece, accompanied by an increase in the adhesion component of the friction force and a gradual increase in the roughness of both the tool and the workpiece; contact interaction processes are rapidly intensified at the last (critical) stage of wear, cutting forces increase, which affects a noticeable deterioration in the quality of the surface layer of the workpiece [82]. (Figure 8 is provided in the file) 

Point 3: In Figure 10(a) and (b), authors showed the effect of temperature on the coefficient of friction. It is suggested that authors should provide explanations for the temperature effect and discuss the mechanisms.

Response 3: Thank you, the text is revised.

After lines 594-599:

• COF curve does not have sharp bursts throughout the entire path, and its value remains at a low level from 0.3 to 0.5 (COF value upon heating has even lower values than those, which had a similar sample when tested without heating);
• COF stabilizes even more and amounts to a little less than 0.45 after passing a path of 150 m. The sample containing 80% HSS, 20% TiC, and 5% Al₂O₃ demonstrates an in termediate value among the CPHSS samples in terms of tribological characteristics.

Discussion concerning the temperature effect and the mechanism were added:

The results of testing a sample of 80% HSS and 20% TiC (Figure 6, curve 2) showed the maximum increase in the wear of the contact zone after 15 min of milling and by the end of the tests. The volume of abrasion even slightly exceeds the wear of a sample from traditional HSS. The intensity of material destruction under an abrasive action is largely determined by the ratio of the counterbody hardness and the test metal surface hardness in the contact zone. A sharp increase in the wear rate of an 80% HSS and 20% TiC sample can be associated with a decrease in the hardness of its surface layer at a certain moment. The specific structure of CPHSS (Figure 5), containing a significant amount of refractory inclusions of polyhedral and fragmentary shapes, undissolved in the steel bond, suggests that the level of hardness (and the intensity of abrasive wear directly related to it) of such a material is determined by the degree of preservation of the high-hardness carbide phase. It is most likely that over time and an increase in the volume of abrasion, hard and, at the same time, very brittle TiC particles (their ductility increases at temperatures above 600˚C) are not retained in the steel bond and crumble, significantly changing the conditions of contact interaction between the tool material and counterbody. For the other two studied CPHSS samples (Figure 6, curves 3 and 4), a high degree of safety in the steel bond of high-hardness components is ensured throughout the entire test cycle. However, it is too early to conclude the prospects of one or another CPHSS variant based on evaluating the resistance to abrasion without thermal action.

Round 2

Reviewer 1 Report

All questions answered and paper can be accepted